1. Field of Invention
The present invention generally relates to systems and methods for administering intracavitary brachytherapy to subject.
2. Description of Related Art
Endometrial carcinoma, a malignant adenocarcinoma of the glandular epithelium lining the inner wall of the uterus, is one of the most common and serious disorders affecting the endometrium of post-menopausal women. Endometrial carcinomas represent an increasingly frequent tumor occurrence in industrialized countries. For example, in 1997, an estimated 170,000 new cases of endometrial carcinoma were diagnosed worldwide. The high occurrence of this malignancy necessitates the development of new therapeutic treatment alternatives. Moreover, early eradication of the carcinoma generally results in a more favorable prognosis for the patient. While surgical removal of the tumor is a preferred method of treatment, there may be some situations when a patient is unable to tolerate surgery. In some situations, a physician may prescribe one or more courses of preoperative radiation therapy. In yet further situations, surgery may be contraindicated or, particularly in the case of early stage carcinoma, even unnecessary. Additionally, it may be advisable for a patient who has undergone surgery to remove the tumor to undergo one or more courses of radiation therapy to eradicate any remaining tumor cells that may not have been excised.
Radiation therapy is used extensively to treat endometrial malignancies, either pre-operatively, as adjuvant therapy after surgery for patients with greater than stage IA disease, as primary therapy for patients unable to tolerate surgery, or to treat recurrences following surgery. Radiation therapy has been used for uterine cancers for over a century, and may be administered as either external beam treatment, brachytherapy, or both. In some cases, curative intracavitary brachytherapy may represent the most desirable treatment option. Curative intracavitary brachytherapy is frequently used to treat malignancies of the vagina, cervix, and endometrium (the lining of the uterus). Treatment of the endometrium by intracavitary brachytherapy may be referred to herein as intrauterine brachytherapy. While early stage tumors are more responsive to intracavitary implants, more extensive tumors may require treatment with interstitial implants and may involve a combination of external beam radiation therapy and intracavitary and/or interstitial brachytherapy.
Brachytherapy may also be described according to the length of time that a procedure is performed. Low dose rate (LDR) treatments typically require several days if the radioactive sources are temporarily placed in tissue. In some cases, permanent or semi-permanent implants may be preferred, wherein the materials remain in the tissue for a substantial portion of time. During most LDR brachytherapy procedures, a dose of radiation in the range of about 0.4-0.8 Gy/hr is administered. High dose rate (HDR) brachytherapy typically uses high specific activity gamma-emitting radionuclides to deliver a much greater dose (usually >0.4 Gy/min) of radiation to the site than what is administered using LDR brachytherapy. As such, HDR brachytherapy procedures are shorter in duration, and usually last less than an hour. HDR brachytherapy allows precise delivery of the radiation dose prescribed by the physician. The short treatment times, the amenability to performing HDR procedure on outpatient basis, and accurate radiation delivery and inproved patient comfort and compliance are all advantages of HDR brachytherapy.
Methods of brachytherapy may be broadly described as manual, in which the radioactive material is placed at the body by hand, or remote, in which placement of the radioactive material may be at least partially or entirely automated. An automated device that may be used to place a radioactive material during a brachytherapy procedure is typically referred to in the art as “a remote afterloader”. A representative, though non-limiting, example of a remote afterloader is the VariSource® remote afterloader manufactured by Mick Radio-Nuclear Instruments, Inc.
The basic approaches that are used to deliver intracavitary brachytherapy for gynecologic cancer include, but are not limited to, disposable afterloading Heyman capsules or tandems with colpostats.
Heyman capsules are described in “An aid to computerization of Heyman afterloading system.” by Boles and Cook, which is fully incorporated herein by reference, and are available commercially. Heyman Capsules are especially suited to a large uterus, and the current practice is to load as many capsules into the uterus as possible, to stretch the uterus and obtain the best isodose profile. Heyman capsules are available in diameters of 6, 8 and 10 mm and lengths of 2-3 cm. Heyman capsules may be introduced into the uterus, through the dilated cervix, using inactive metallic guides. Typically, at least four Heyman capsules are inserted during a procedure, and often a physician may decide that as many as ten may be necessary. A problem encountered with Heyman capsules is that they have relatively thick stems. This may require continued dilation of the cervical canal (such as, for example, with Hegar dilators) after a few capsules have been inserted, resulting in added discomfort to the patient. Furthermore, since Heyman capsules are numbered, they should always be removed in the reverse order in which they were inserted to avoid jamming.
For patients with small uteri, it may be preferable to administer intrauterine brachytherapy with one or more tandems (in lieu of Heyman capsules) with attached colpostats (which may also be referred to as “ovoids”). Similar techniques used to administer brachytherapy for cervical cancer, such as the Henshke or Fletcher-Suit systems, may be used for intrauterine brachytherapy applications. Tandems are placed in the uterus using a device known as a “tandem and ovoid” applicator. A tandem and ovoid applicator includes a hollow metal tube (the tandem) that is inserted through the cervix into the endometrial cavity. The tandem is about 10 inches long and about as thin as a pencil. The ovoids are hollow metal capsules that are small enough to fit in the vagina and through the dilated cervix. The tandem and ovoid applicator are usually surgically inserted, under anesthesia, in a procedure that may take as long as thirty minutes. As such, intrauterine brachytherapy procedures using tandem and ovoids techniques may require the patient to remain hospitalized, sometimes as long as two days. Radiation therapy is given through the tandem and ovoid applicator by placing radioactive capsules or seeds inside the hollow portions of the applicator.
The American Brachytherapy Society recommends that the treatment plan for high-dose-rate brachytherapy for endometrial carcinoma should be optimized to conform to the target volume as much as possible, and that applicator selection should be based on patient and target volume geometry. Ideally, an appropriate applicator that will administer a substantially homogeneous dose of radiation (i.e. an isodose) to the entire uterus should be selected. These recommendations are set forth in Nag et al., “The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for carcinoma of the endometrium.” International Journal of Radiation Oncology Biology Physics, 2000, Volume 48, pages 779-790, which is incorporated by reference as though fully set forth herein.
While the brachytherapy systems and methods described above are widely used, they typically, due in part to anatomical variations in the shape, thickness, orientation and size of the uterus of individual patients, do not deliver a substantially uniform isodose to the entire uterus. Moreover, because of the somewhat invasive nature of the above mentioned systems, and because patients may typically require multiple treatments, a system that shortens the procedure time and eases the discomfort experienced by the patient, and is thus more readily tolerated, would be advantageous.
Interstitial brachytherapy systems have been used to administer postoperative LDR or HDR brachytherapy to the tissue surrounding a resection cavity. U.S. Pat. No. 5,913,813 entitled “Double-wall balloon catheter for treatment of proliferative tissue” and U.S. Pat. No. 6,413,204 entitled “Interstitial brachytherapy apparatus and method for treatment of proliferative tissue diseases” describe an interstitial brachytherapy apparatus for delivering radioactive emissions to a surgical resection cavity including a central bitumen catheter with an inflatable balloon coupled to the distal end of the apparatus. U.S. Pat. No. 5,931,774 entitled “Inflatable devices for tumor treatment” describes an implantable LDR brachytherapy catheter with distal inflatable balloon that is inflated with a radioactive treatment fluid. While these systems work well for interstitial brachytherapy applications, their use in intrauterine applications may be limited due to variations in the shape, thickness, orientation and size of the uterus of individual patients.
There is still a need for a brachytherapy system that may be used to deliver a radioactive source residing in a flexible catheter that may easily be introduced into the uterus, where the apparatus maintains the catheter and the radioactive source in a position that delivers a substantially uniform radiation isodose with a desired intensity to the entire uterus.